Polyacetal copolymer and composition thereof

ABSTRACT

The present invention relates to a polyacetal copolymer comprising a polyoxymethylene group (A) and a vinyl polymer group (B), the copolymer having a structure of the formula (I): 
     
         A.sub.n --X--B                                             (I) 
    
     wherein X is a terminal group of B and represents a binding group derived from a compound having at least two carbon atoms and 1 to 4 groups selected from hydroxyl, carboxyl, ester, amino and alkoxy groups, and A n  means that A is present in the quantity of n times in number, and bonds to X, in which n=1 to 4, and the copolymers has a number average molecular weight of 10,000 to 500,000; a process for the production of said copolymer; and a composition comprising said copolymer and a polyvinyl polymer and/or polyoxymethylene.

FIELD OF THE INVENTION

The present invention relates to a polyacetal copolymer having excellentsurface decorating performance. More specifically, the present inventionrelates to a polyacetal copolymer which permits direct coating andprinting on a molded article made of the polyacetal copolymer withoutacid treatment or primer treatment of the molded article surface, and acomposition thereof.

BACKGROUND OF THE INVENTION

Polyacetal resin is widely used in a variety of fields such as in thefield of automobile parts, etc., because of its excellent mechanicalstrength, abrasion resistance, creep properties, fatigue properties andelectrical properties.

In general, however, polyacetal resin has a problem in that surfacedecorating such as printing, coating, etc., is difficult due to its poorsurface activity. Therefore, several attempts have been made to improveits surface decorating performance. For example, there has been proposeda method of preliminary treatment with acidic chemicals of phosphoricacid and sulfuric acid, a method of using a cellulose-based coatingcomposition as a primer, a method of using a primer prepared bydissolving a chlorinated polyolefin resin in a chlorine-containingsolvent, and some other methods have been proposed to improve surfacedecorating performance.

However, these methods are not fully satisfactory due to problems suchas the requirement of additional processing steps for acid treatment andwashing with water, deformation of the material due to a step of dryingthe coating, harmfulness of a chlorine-containing solvent, etc.

An object of this invention is to overcome the above problems associatedwith the prior methods such as the requirement of additional processingsteps, deformation of the material, harmfulness of a chlorine-containingsolvent, etc. That is, the present invention seeks to simplify a coatingstep and to reduce production costs so that a decorative article havinga coating with high bond strength can be produced free from materialdeformation by only applying a coating composition directly to apolyacetal molded article surface without any chemical treatment orprimer treatment and drying the coating.

An acetal polymer is usually produced by homopolymerization offormaldehyde or trioxane, or by copolymerization of formaldehyde ortrioxane with a cyclic ether.

For example, U.S. Pat. No. 3,218,295 discloses the Polymerization offormaldehyde in the presence of a polyalkylene glycol or a vinylcompound such as a vinyloxyethylamine/methyl methacrylate copolymer or avinyloxyethylamine/isobutyl methacrylate copolymer. U.S. Pat. No.3,732,333 also discloses the polymerization of formaldehyde in thepresence of a living polymer of a vinyl compound such as styrene ormethyl methacrylate.

However, polymers obtained by the above polymerization processes canhardly give the surface decorating performance referred to in thepresent invention. Further, the mechanical properties inherentlybelonging to a polyacetal resin are degraded to a great extent.

The polymer of the above U.S. Pat. No. 3,732,333 also has a defect inthat the polymer is a mixture of a vinyl polymer with an aldehydehomopolymer due to its polymerization process in which formaldehyde ispolymerized in the presence of a living polymer as a polymerizationinitiator.

DISCLOSURE OF THE INVENTION

The present inventors have made a diligent study to overcome the aboveproblems, and found that a novel polyacetal copolymer comprising apolyoxymethylene and a specific vinyl compound and a composition thereofgive an excellent surface decorating performance to permit coating andprinting without any preliminary treatment with a chemical or primertreatment, and this invention has been completed on the basis of thisfinding.

The first and second aspects of this invention are directed to thefollowing:

a polyacetal copolymer which is a copolymer comprising apolyoxymethylene group (A) and a vinyl polymer group (B), having astructure of the formula (I):

    A.sub.n --X--B                                             (I)

wherein X is a terminal group of B and represents a binding groupderived from a compound having at least two carbon atoms and 1 to 4groups selected from hydroxyl, carboxyl, ester, amino and alkoxy groups,and A_(n) means that A is present in the quantity of n times in number,and bonds to X, in which n=1 to 4, and the polyacetal copolymer has anumber average molecular weight of 10,000 to 500,000; and

a process for the production of the above polyacetal copolymer whichcomprises homopolymerizing formaldehyde or trioxane in the presence, asa molecular weight regulator, of a vinyl polymer having 1 to 4 groupsselected from hydroxyl, carboxyl, amino, ester and alkoxy groups at oneterminal thereof or copolymerizing formaldehyde or trioxane with acyclic ether in the presence of the above molecular weight regulator.

A third aspect of this invention is directed to a polyacetal resincomposition, comprising:

(a) a polyacetal copolymer having a structure of the above formula (I),(b) a polyvinyl polymer having a structure of the formula (III):##STR1## wherein R₁, is hydrogen or alkyl, R₂, is hydrogen, phenyl,cyano, chloro, acetyl or alkyl ester, and z is 10 to 5,000, and

(c) a polyoxymethylene;

the composition containing, per 100 parts by weight of the (a)polyacetal copolymer, 0 to 500 parts by weight of the (b) polyvinylpolymer and 0 to 1,700 parts by weight of the (c) polyoxymethylene, andcontaining (a) and at least one of (b) and (c).

PREFERRED EMBODIMENTS OF THE INVENTION

The polyacetal copolymer of this invention is a novel copolymercomprising a polyoxymethylene group (A) and a vinyl polymer group (B)and having a structure of the formula (I):

    A.sub.n --X--B                                             (I)

wherein X is a terminal group of B and represents a binding groupderived from a compound having at least two carbon atoms and 1 to 4groups selected from hydroxyl, carboxyl, ester, amino and alkoxy groups,and A_(n) means that A is present in the quantity of n times in number,and bonds to X in which n =1 to 4. The polyoxymethylene group aboveencompasses a polyoxymethylene homopolymer and a polyoxymethylenecopolymer.

The polyoxymethylene homopolymer above is a polymer having oxymethylenerecurring units of --CH₂ O--. The polyoxymethylene copolymer above isalso a polymer having the following oxyalkylene units: ##STR2##

wherein each R₀ is independently hydrogen, alkyl or aryl, and m is 2 to6. These oxyalkylene units are inserted into a chain of the oxymethyleneunits at random.

The content of the oxyalkylene units in the polyoxymethylene copolymeris 0.05 to 50 moles, preferably 0.1 to 20 moles per 100 moles of theoxymethylene units.

The polyacetal copolymer of this invention which has a hydroxyl group inthe terminal portion of the polyoxymethylene chain immediately after thepolymerization is unstable. When the polyoxymethylene group is apolyoxymethylene homopolymer, the terminal hydroxyl group is convertedto a stable group by a known method such as esterification,etherification, urethanation, etc., before practical use of thepolyacetal copolymer. When the polyoxymethylene group is apolyoxymethylene copolymer, the terminal group is treated in the sameway as in the case of the polyoxymethylene homopolymer or the terminalunstable group is removed by hydrolysis before practical use.

The structure of the polyacetal copolymer of this invention isidentified in the following manner. That is, when the polyacetalcopolymer is hydrolyzed in an acidic aqueous solution, the oxymethylenerecurring unit portion becomes formaldehyde, and the oxyalkylene unitportion inserted into the polyoxymethylene copolymer becomes an alkyleneglycol of the following formula: ##STR3## In addition, the vinyl polymergroup becomes a vinyl polymer of the formula (IV):

    X'--B                                                      (IV)

wherein X' represents 1 to 4 hydroxyl or carboxyl groups, since the bondbetween X and the polyoxymethylene group (A) in the formula (I) isbroken.

The formaldehyde and the alkylene glycol are analyzed and determined bymeans of gas chromatography, liquid chromatography, or the like. Thevinyl polymer of formula (IV) is also analyzed and determined by meansof chromatography, IR, NMR, GPC, or the like.

The number average molecular weight of the polyacetal copolymer of thisinvention is the same as those of known high-molecular-weightpolyacetals, and it is in the range of about 10,000 to 500,000. Thelower limit of the number average molecular weight is limited by theproperties of the polyacetal copolymer, and the upper limit thereof islimited by the molding processability of the polyacetal copolymer. Thenumber average molecular weight of the polyacetal copolymer isdetermined in the following manner. That is, the number averagemolecular weight of 100,000 or less is determined by an osmotic pressuremethod or by an end-group analysis method, and the number averagemolecular weight of 100,000 or more is determined by relating a weightaverage molecular weight determined by a light-scattering method with anelution curve determined by a gel permeation chromatography (GPC).

The A segment of the polyacetal copolymer of this invention encompassesa polyoxymethylene homopolymer and a polyoxymethylene copolymer. In thepolyoxymethylene copolymer, the oxyalkylene unit to be inserted into thepolymer composed mainly of oxymethylene units is represented by theformula: ##STR4## wherein each R₀ is independently hydrogen, alkyl oraryl, and m is 2 to 6. Examples of the oxyalkylene unit are anoxyethylene unit --CH₂)₂ O--, an oxypropylene unit ##STR5## anoxytrimethylene unit --CH₂)₃ O--, an oxytetramethylene unit --CH₂)₄)--,an oxybutylene unit ##STR6## an oxyhexamethylene unit --CH₂)₆ O--, andan oxyphenylethylene unit ##STR7## Of these oxyalkylene units, theoxyethylene unit and the oxytetramethylene unit are particularlypreferred in view of improvement in physical properties of thepolyacetal copolymer.

The polyoxymethylene group (A) as one segment of the polyacetalcopolymer of this invention has a number average molecular weight ofabout 5,000 to about 495,000. The lower limit of the number averagemolecular weight is limited by physical properties of the polyacetalcopolymer, and the upper limit thereof is limited by the moldingprocessability of the polyacetal copolymer.

The vinyl polymer group (B) as another segment of the polyacetalcopolymer of this invention is a compound having a structure of theformula (II): ##STR8## wherein R₁ is hydrogen or alkyl, R₂ is hydrogen,phenyl, cyano, chloro, acetyl, alkyl ester, and l is 10 to 5,000.Compounds having a structure of the formula (II) are classified into thefollowing three groups.

Examples of the first group are a styrene polymer, an acrylonitrilepolymer, a vinyl chloride polymer, an ethylene polymer, a vinyl acetatepolymer, a styrene/acrylonitrile copolymer, a styrene/vinyl chloridecopolymer, an ethylene/vinyl acetate copolymer, a styrene/ vinyl acetatecopolymer, an acrylonitrile/vinyl acetate copolymer and a vinylchloride/vinyl acetate copolymer.

Examples of the second group are a polymer of an acrylic or amethacrylic ester and a copolymer of an acrylic ester and a methacrylicester.

Typical examples of the acrylic ester are methyl acrylate, ethylacrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate,iso-butyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-octylacrylate, 2-ethylhexyl acrylate, n-lauryl acrylate, iso-lauryl acrylate,n-stearyl acrylate, iso-stearyl acrylate, acrylamide, dimethylaminoethylacrylate glycidyl acrylate, and cyclohexyl acrylate. Typical examples ofthe methacrylic ester are methyl methacrylate, ethyl methacrylate,n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate,iso-butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate,n-octyl methacrylate, 2-ethylhexyl methacrylate, n-lauryl methacrylate,iso-lauryl methacrylate, n-stearyl methacrylate, iso-stearylmethacrylate, dimethylaminoethyl methacrylate, glycidyl methacrylate,and cyclohexyl methacrylate.

Examples of the third group are copolymers of an acrylic or methacrylicester with styrene, acrylonitrile, ethylene, vinyl acetate or vinylchloride.

The vinyl polymer group has a number average molecular weight of about1,000 to about 300,000, and those having a number average molecularweight of 1,000 to 100,000 are preferred in view of ease in productionand purification.

In the polyacetal copolymer of this invention, the binding group (X)which binds the polyoxymethylene group (A) and the vinyl polymer group(B) is selected from a variety of hydrocarbon moieties which have atleast 2 carbon atoms and 1 to 4 groups selected from hydroxyl, carboxyl,amino ester and alkoxy groups. A binding group having a structure of thefollowing formula is preferred in view of ease in production: ##STR9##

wherein each D is ##STR10## Y is oxygen or sulfur, a is 0 to 3, and B isa vinyl polymer group.

The polyacetal copolymer of this invention is specifically illustratedwith structural formulae as follows:

(1) n =1 in the formula (I): ##STR11## (2) n=2 in the formula (I):##STR12## (3) n=3 in the formula (I): ##STR13## (4) n=4 in the formula(I):

In the above structural formulae, R₁ is hydrogen or alkyl, R₂ ishydrogen, phenyl, cyano, chloro, acetyl or alkyl ester, l is 10 to5,000, each of R₃ to R₆ is independently hydrogen, alkyl or acyl, eachof n' and m' is an integer, each D is ##STR14## and Y is oxygen orsulfur.

In addition, the structural formula --OCH₂)_(n') --(OCH₂ CH₂)_(m') ]means that m' mol of the oxyethylene units are inserted in n' mol of theoxymethylene units, and does not define the distribution of theoxymethylene units in the polymer chain.

The production of the polyacetal copolymer of this invention will beexplained below.

The polyacetal copolymer of this invention is produced byhomopolymerizing formaldehyde or trioxane in the presence, as amolecular weight regulator, of a vinyl polymer which has a structure ofthe formula (II): ##STR15##

wherein R₁ is hydrogen or alkyl, R₂ is hydrogen, phenyl, cyano, chloro,alkyl ester, and l is 10 to 5,000, and which has 1 to 4 groups selectedfrom hydroxyl, carboxyl, ester, amino and alkoxy groups at one terminalportion thereof or by copolymerizing formaldehyde or trioxane with acyclic ether in the presence of the above molecular weight regulator.

Examples of the molecular weight regulator used in this invention areillustrated with structural formulae as follows:

(1) First group ##STR16## (2) Second group ##STR17## (3) Third group##STR18## (4) Fourth group ##STR19##

In the above formulae, each of R₇ to R₁₀ is independently hydroxyl,alkoxy, ester, carboxyl or amino.

It is desirable to purify the above molecular weight regulators bydistillation, adsorption, drying, etc., in advance of the use for thepolymerization. These molecular weight regulators may be used alone orin combination.

In the homopolymerization in this invention, fully purified formaldehydeor trioxane is used as a starting material. An anionic polymerizationcatalyst is mainly used for the homopolymerization of formaldehyde, anda cationic polymerization catalyst is used for the homopolymerization oftrioxane.

In the copolymerization in this invention, fully purified formaldehydeor trioxane is used as a starting material, and these starting materialsare copolymerized with a cyclic ether in the presence of a cationicpolymerization catalyst.

Examples of a first group of the cyclic ether to be copolymerized withthe above starting materials are alkylene oxides of the formula:##STR20## wherein each R₀ is independently hydrogen, alkyl or aryl, andm is 2 to 6, such as ethylene oxide, propylene oxide, butylene oxide,epichlorohydrin, styrene oxide, oxetane, 3,3-bis(chloromethyl)oxetane,tetrahydrofuran and oxepane. Of these alkylene oxides, ethylene oxide isparticularly preferred.

Examples of a second group of the cyclic ether are cyclic formals of thefollowing formula: ##STR21## such as ethylene glycol formal, propyleneglycol formal, diethylene glycol formal, triethylene glycol formal,1,4-butanediol formal, 1,5-pentanediol formal, and 1,6-hexanediolformal. Of these cyclic formals, ethylene glycol formal, diethyleneglycol formal and 1,4-butanediol formal are particularly preferred.

The amount of the cyclic ether per 100 parts by weight of the startingmaterial is 0.03 to 100 parts by weight, preferably 0.1 to 50 parts byweight.

The anionic polymerization catalyst and the cationic polymerizationcatalyst for use in the homopolymerization and copolymerization in thisinvention are as follows.

Typical examples of the anionic polymerization catalyst are alkalimetals such as sodium and potassium, alkali metal complex compounds suchas sodium-naphthalene and potassium-anthracene, alkali metal hydridessuch as sodium hydride, alkaline earth metal hydrides such as calciumhydride, alkali metal alkoxides such as sodium methoxide and potassiumt-butoxide, alkali metal carboxylates such as sodium caproate andpotassium stearate, alkaline earth metal carboxylates such as magnesiumcaproate and calcium stearate, amines such as n-butylamine,diethylamine, trioctylamine and pyridine, quaternary ammonium salts suchas ammonium stearate, tetrabutylammonium methoxide anddimethyldistearylammonium acetate, phosphonium salts such astetramethylphosphonium propionate and trimethylbenzylphosphoniumethoxide, tetravalent organic tin compounds such as tributyltinchloride, diethyltindilaurate and dibutyltin dimethoxide, and alkylmetals such as n-butyllithium and ethylmagnesium chloride.

Examples of the cationic polymerization catalyst are Friedel-Crafts typecompounds such as tin tetrachloride, tin tetrabromide, titaniumtetrachloride, aluminum trichloride, zinc chloride, vanadiumtrichloride, antimony pentafluoride, boron trifluoride and borontrifluoride coordination compounds e.g. boron trifluoride diethyletherlate, boron trifluoride acetic anhydrate, boron trifluoridetriethylamine complex compound; inorganic and organic acids such asperchlorate, acetyl perchlorate, hydroxyacetic acid, trichloroaceticacid and p-toluene sulfonate, complex salt compounds such astriethyloxonium tetrafluoroborate, triphenylmethyl hexafluoroantimonate,allyldiazonium hexafluorophosphate and allyldiazonium tetrafluoroborate,and alkyl metals such as diethylzinc, triethylaluminum anddiethylaluminum chloride.

The amount of the above anionic polymerization catalyst and the cationicpolymerization catalyst per 100 parts by weight of the starting materialis 0.0005 to parts by weight. The homopolymerization or copolymerizationis carried out in the absence of a solvent or in the presence of anorganic solvent.

Examples of the organic solvent are aliphatic hydrocarbons such asn-pentane, n-hexane, n-heptane, n-octane, cyclohexane and cyclopentane,aromatic hydrocarbons such as benzene, toluene and xylene, halogenatedaliphatic hydrocarbons such as methylene chloride, chloroform, carbontetrachloride, ethylene chloride and trichloroethylene, and halogenatedaromatic hydrocarbons such as chlorobenzene and o-dichlorobenzene. Theseorganic solvents may be used alone or in combination. The molecularweight regulator is used by homogeneously dissolving or dispersing it inthe reaction system. The concentration of the molecular weight regulatorin the system can be easily determined by an experiment depending uponthat molecular weight required for a desired polyacetal copolymer.

The reaction temperature is usually set at a temperature between -20° C.and 230° C., and it is preferably set between 20° C. and 210° C. when nosolvent is used, and between -10° C. and 120° C. when an organic solventis used.

The reaction time is not specially limited, and may be set for a periodof time between 5 seconds and 300 minutes.

The homopolymerization or copolymerization is terminated by adding ashort-stop to the reaction system after a predetermined period of time.The resultant polymer is stabilized by removing its unstable terminalportion by hydrolysis or by blocking the unstable terminal portion by anesterification method, etc. A stabilizer, etc., may be further added tothe stabilized polyacetal copolymer as required before practical use.

The polyacetal copolymer of this invention provides for an excellentsurface decorating performance even if used alone, and if also exhibitsan excellent performance when used in combination with anothercomponent, as will be described below.

The composition of this invention will be explained below.

The polyacetal resin composition of the present invention comprises (a)a polyacetal copolymer of this invention, (b) a polyvinyl polymer havinga structure of the formula (III): ##STR22## wherein R₁ ' is hydrogen oralkyl, R₂ ' is hydrogen phenyl, cyano, chloro, acetyl or alkyl ester,and z is 10 to 5,000, and (c) a polyoxymethylene; the compositioncontaining, per 100 parts by weight of the (a) polyacetal copolymer, 0to 500 parts by weight of the (b) polyvinyl polymer and 0 to 1,700 partsby weight of the (c) polyoxymethylene, and containing (a) and at leastone of (b) and (c).

The polyvinyl polymer having a structure of the formula (III) for use inthe polyacetal resin composition of this invention is classified intothree groups.

Examples of the first group are a styrene polymer, an acrylonitrilepolymer, a vinyl chloride polymer, an ethylene polymer, a vinyl acetatepolymer, a styrene/acrylonitrile copolymer, a styrene/vinyl chloridecopolymer, an ethylene/vinyl acetate copolymer, a styrene/vinyl acetatecopolymer, an acrylonitrile/vinyl acetate copolymer, a vinylchloride/vinyl and acetate copolymer.

Examples of the second group are a polymer of an acrylic or methacrylicester and a copolymer of an acrylic ester and a methacrylic ester.

Typical examples of the acrylic ester are methyl acrylate, ethylacrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate,iso-butyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-octylacrylate, 2-ethylhexyl acrylate, n-lauryl acrylate, iso-lauryl acrylate,n-stearyl acrylate, iso-stearyl acrylate, 2-hydroxylethyl acrylate,acrylamide, dimethylaminoethyl acrylate, glycidyl acrylate, andcyclohexyl acrylate. Typical examples of the methacrylic ester aremethyl methacrylate, ethyl methacrylate, n-propyl methacrylate,iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate,sec-butyl methacrylate, tert-butyl methacrylate, n-octyl methacrylate,2-ethylhexyl methacrylate, n-lauryl methacrylate, iso-laurylmethacrylate, n-stearyl methacrylate, iso-stearyl methacrylate,2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,dimethylaminoethyl methacrylate, glycidyl methacrylate, and cyclohexylmethacrylate.

Examples of the third group are copolymers of an acrylic or methacrylicester with styrene, acrylonitrile, ethylene, vinyl acetate or vinylchloride.

The polyoxymethylene for use in the polyacetal resin composition of thisinvention is classified into two groups such as a homopolymer and acopolymer. The homopolymer in the first group is a polymer obtained byhomopolymerization of formaldehyde or trioxane. The copolymer in thesecond group is a polymer obtained by copolymerization of formaldehydeor trioxane with a cyclic ether. Examples of the cyclic ether arealkylene oxides such as ethylene oxide, propylene oxide and butyleneoxide and cyclic formals such as 1,4-butanediol formal, ethylene glycolcyclic formals such as 1,4-butanediol formal, ethylene glycol formal anddiethylene glycol formal.

The amount of the polyvinyl polymer is required to be in the range of 0to 500 parts by weight per 100 parts by weight of the polyacetalcopolymer. When this amount exceeds 500 parts by weight, the mechanicalproperties of polyacetal such as creep properties, fatigue properties,lubrication properties, etc., are degraded to a great extent. The aboveamount of the polyvinyl polymer is preferably 5 to 200 parts by weight.

When no polyvinyl polymer is incorporated, the polyacetal resincomposition is required to contain the polyacetal copolymer and thepolyoxymethylene.

The amount of the polyoxymethylene is required to be in the range of 0to 1,700 parts by weight per 100 parts by weight of the polyacetalcopolymer. When this amount exceeds 1,700 parts by weight, the surfacedecorating performance is degraded, and this tendency becomes dominantwhen no polyvinyl polymer is added. The above amount of thepolyoxymethylene is preferably 0 to 1,500 parts by weight. When nopolyoxymethylene is incorporated, the polyacetal resin composition isrequired to contain the polyacetal copolymer and the polyvinyl polymer.

In the polyacetal resin composition of this invention, the polyacetalcopolymer functions as a compatibilizer for the polyoxymethylene and thepolyvinyl polymer, and the composition of this invention is oftenobtained as a homogeneous polymer alloy.

Depending upon the desired use and the intended purpose, the compositionof this invention may contain conventional auxiliaries such as a thermalstabilizer, an antioxidant, a parting agent, a weatherability improver,an antistatic agent, a colorant, a reinforcing agent, a surfactant andan inorganic filler.

The composition of this invention is, in general, melt-mixed with anextruder, and it can be produced into molded articles by a conventionalmolding method such as by injection molding or by extrusion. The moldingis usually carried out at a temperature between 170° C. and 300° C.

EXAMPLES

the present invention will be more specifically explained by referenceto the following Examples, which, however, shall not limit thisinvention.

The following measurements were carried out, and data therefrom areshown in the Examples.

Reduced viscosity: A value obtained by a measurement of 0.5 g/dl of apolymer in a p-chlorophenol/ tetrachloroethylene (weight ratio 1 : 1)solution at 60° C.

R_(v222) An index for the thermal stability of a polymer. A heating losswhen a polymer whose unstable terminal portion has been stabilized withacetic anhydride is heated under vacuum at 222° C. for 60 minutes. Ahigher value for R_(v222) shows better thermal stability.

Crosscut test: Test for bond strength of a coating. The measurement wascarried out according to JIS K 5400. A coating on a test piece was crosscut lengthwise and widthwise 11 times at intervals of 1 mm each to form100 squares within a 1 cm² square. A cellophane tape was appliedthereto, and peeled off. The bond strength of the coating was evaluatedon the basis of the number of 1 mm×1 mm squares. A smaller number of thesquares which were peeled off shows a higher bond strength. A coatingsurface having higher bond strength has a better decorating performance.

Abrasion wear: A measure of mechanical properties. The measurement wascarried out according to JIS K 7218A by using a pressing material S45Cunder a surface pressure of 1 Kg/cm², a linear speed of 24 cm/sec and arun distance of 50 km. Less abrasion wear shows better mechanicalproperties.

MI: A measure for molecular weight. The measurement was carried outaccording to the conditions of ASTM D-1238 E.

EXAMPLE 1

(1) Production of Polyacetal Copolymer

Fully dehydrated and dried p-formaldehyde was pyrolyzed at 150° C., andpassed through a cooling trap several times to give a formaldehyde gashaving a purity of not less than 99.9%. 300 Grams/hour of theformaldehyde gas was introduced into 1,500 g of toluene containing1.0×10⁻⁴ mol/l of tetrabutylammonium acetate and 8.1×10⁻³ mol/l of##STR23## (polybutyl acrylate whose one terminal was modified tohydroxyl, M_(n) =9,000, "PBA-9" hereinafter) as a molecular weightregulator. Simultaneously with the introduction of the formaldehyde,toluene containing 1.0×10⁻⁴ mol/l of tetrabutylammonium acetate and8.1×10⁻³ mol/l of PBA-9 was continuously introduced at a rate of 1,500g/hour for 4 hours. The formaldehyde gas was also continuouslyintroduced at a rate of 300 g/hour, during which the polymerizationtemperature was maintained at 60° C. Toluene containing a polymer wascontinuously extracted in such an amount that met with the supply, andthe polymer was isolated by filtration. The polymer was fully washedwith hot acetone and dried under vacuum at 60° C. to give 1,050 g of awhite polymer. This polymer was subjected to extraction in chloroform at60° C. for 5 hours to show an extraction of PBA-9.

(2) Determination of Structure of Polyacetal Copolymer

5 Grams of the polyacetal copolymer obtained in step (1) of Example (1)above was dispersed in 95 g of a 0.1 N hydrochloric acid aqueoussolution, and the resultant dispersion was heated at 90° C. for 2 hours.This heating procedure converted the oxymethylene-recurring unitportions back to formaldehyde under complete hydrolysis. Meanwhile, themolecular weight regulator did not undergo hydrolysis under the aboveconditions. Then, the resultant solution was neutralized with a 0.5 Nsodium hydroxide aqueous solution, the solution was evaporated underatmospheric pressure, and the remainder was extracted by adding 50 g oftetrahydrofuran. The resultant extract liquid was quantitativelydetermined by liquid chromatography, whereby 13.4×10⁻⁴ moles of PBA-9per mole of formaldehyde was detected.

The polyacetal copolymer obtained in step (1) was subjected to infraredabsorption spectrum analysis to the determine ester groups, whereby9.42×10⁻² moles of ester groups ##STR24## from PBA-9 per mole offormaldehyde were detected.

50 Grams of the polyacetal copolymer obtained in step (1), 500 g ofacetic anhydride and 0.1 g of sodium acetate were together heated at139° C. for 3 hours for terminal acetylation, and 46 g of the polymerwas recovered. The polymer was subjected to infrared absorption spectrumanalysis to determine the ester groups, whereby 9.48×10⁻² moles of theester groups per mole of formaldehyde were detected. The ester groupsdetermined by this analysis include the ester group ##STR25## derivedfrom PBA-9 and the ester group ##STR26## corresponding to the terminalhydroxyl group of the polymer.

The above analysis and results show that the polymer had an oxymethylenechain of which the number average molecular weight was 18,300, and thepolymer was a polyacetal copolymer having the following structure:##STR27##

(3) Determination of Physical Properties and Coatability of PolyacetalCopolymer

The polyacetal copolymer obtained in step (1) had a reduced viscosity of1.34, which was the desired amount. The polyacetal copolymer exhibitedan R_(v222) of 99% and had an excellent thermal stability. A stabilizerwas added to the polyacetalcopolymer which had been terminal-stabilized,the mixture was molded, and the resultant article was coated with aurethane-based coating composition. The coating was dried at apredetermined temperature for a predetermined period of time. Theresultant test piece was subjected to a crosscut test to evaluate itscoatability. The results of the crosscut test showed excellentcoatability and the number of squares peeled off was 0/100.

EXAMPLE 2 (1) Production of Polyacetal Copolymer

Fully dehydrated and dried p-formaldehyde was pyrolyzed at 150° C., andpassed through a cooling trap several times to give a formaldehyde gashaving a purity of not less than 99.9%. 300 grams/hour of theformaldehyde gas was introduced into 1,500 g of toluene containing1.0×10⁻⁴ mol/l of tetrabutylammonium acetate and 5.35×10⁻³ mol/l of##STR28## (polybutyl methacrylate whose one terminal end was modified tohydroxyl M_(n) =8,800, "PBA-2" hereinafter) as a molecular weightregulator. Simultaneously with the introduction of the formaldehyde,toluene containing 1.0×10⁻⁴ mol/l of tetrabutylammonium acetate and5.35×10⁻³ mol/l of PBA-2 was continuously introduced at a rate of 1,500g/hour for 4 hours. The formaldehyde gas was also continuouslyintroduced at a rate of 300 g/hour, during which the polymerizationtemperature was maintained at 60° C. Toluene containing a polymer wascontinuously extracted in such an amount that met with the supply, andthe polymer was isolated by filtration. The polymer was fully washedwith hot acetone and dried under vacuum at 60° C. to give 1,120 g of awhite polymer. This polymer was subjected to extraction in chloroform at60° C. for 5 hours to show no extraction of PBA-2.

(2) Determination of Structure of Polyacetal Copolymer

5 Grams of the polyacetal copolymer obtained in step (1) was dispersedin 95 g of a 0.1 N hydrochloric acid aqueous solution, and the resultantdispersion was heated at 90° C. for 2 hours. This heating procedureconverted oxymethylene-recurring unit portions back to formaldehydeunder complete hydrolysis. Meanwhile, the molecular weight regulator didnot undergo hydrolysis under the above conditions. Then, the resultantsolution was neutralized with a 0.5 N sodium hydroxide aqueous solution,the solution was evaporated under atmospheric pressure, and theremainder was extracted by adding 50 g of tetrahydrofuran. The resultantliquid extract was determined by liquid chromatography, whereby6.82×10⁻⁴ mol of PBA-2 per mole of formaldehyde was detected.

The polyacetal copolymer obtained in step (1) was subjected to infraredabsorption spectrum analysis to determine the ester groups, whereby46.9×10⁻³ mol of ester groups ##STR29## (iso derived from PBA-2 per moleof formaldehyde were detected.

50 Grams of the polyacetal copolymer obtained in step (1), 500 g ofacetic anhydride and 0.1 g of sodium acetate were together heated at139° C. for 3 hours for terminal acetylation, and 46 g of the polymerwas recovered. The polymer was subjected to infrared absorption spectrumanalysis to determine the ester groups, whereby 48.6×10⁻³ mol of theester groups per mole of formaldehyde were detected. The ester groupsdetermined by this analysis contained the ester group ##STR30## derivedfrom PBA-2 and the ester group ##STR31## corresponding to the terminalhydroxyl group of the polymer.

The above analysis and results show that the polymer had an oxymethylenechain of which the number average molecular weight was 16,200, and thepolymer was a polyacetal copolymer having the following structure:##STR32##

(3) Determination of Physical Properties and Coatability of PolyacetalCopolymer

The polyacetal copolymer obtained in step (1) had a reduced viscosity of1.43, which was the desired amount The polyacetal copolymer exhibited anR_(v222) of 98.9% and had an excellent thermal stability. A stabilizerwas added to the polyacetal copolymer, the mixture was molded, and theresultant article was coated with a urethane-based coating composition.The coating was dried at a predetermined temperature for a predeterminedperiod of time. The resultant test piece was subjected to a crosscuttest to evaluate its coatability. The results of the crosscut testshowed excellent coatability in which the number of squares peeled offwas 0/100.

EXAMPLE 3

The "production of polyacetal copolymer" in Example 1 was repeatedexcept that PBA-9 was replaced with a molecular weight regulator of##STR33## (polymethyl methacrylate whose one terminal portion wasmodified to hydroxyl, M_(n) =16,000). The resultant polymer had areduced viscosity of 1.84 and exhibited R_(v222) of 99.1. The polymeralso had a number average molecular weight of 43,000. Further, thepolymer was found to be a polyacetal copolymer having the followingstructure: ##STR34##

The above polyacetal copolymer was used for the evaluation of thecoatability of an article molded therefrom. In a crosscut test (using aurethane-based coating composition), the molded article showed excellentcoatability in which the number of squares peeled off was 0/100.

EXAMPLE 4

The "production of polyacetal copolymer" in Example 1 was replaced witha molecular weight regulator of ##STR35## (polystyrene whose oneterminal portion was modified to hydroxyl M_(n) =6,000). The resultantpolymer had a reduced viscosity of 1.28 and exhibited an R_(v222) of98.8. The polymer also had a number average molecular weight of 47,400.Further, the polymer was found to be a polyacetal copolymer having thefollowing structure: ##STR36##

The above polyacetal copolymer was used for the evaluation of thecoatability of an article molded therefrom. In a crosscut test (using aurethane-based coating composition), the molded article showed excellentcoatability in which the number of squares peeled off was 0/100.

EXAMPLE 5 (1) Production of Polyacetal Copolymer

A kneader having two Σ-formed stirring blades was charged with 500 g offully purified trioxane, 10 g of ethylene oxide and 165 g of a molecularweight regulator of ##STR37## (polystyrene whose one terminal portionwas modified into hydroxyl, M_(n) =6,000, "PS-5" hereinafter), and thecharged components were heated to 70° C. Then, the kneader was chargedwith 0.25 g of boron trifluoride dibutyl etherate, and the resultantmixture was heated for 35 minutes. Immediately thereafter, 10 g oftributylamine was added to terminate the polymerization. The reactionmixture was taken out of the kneader, and washed with hot acetone togive 460 g of a polyacetal copolymer. This polymer was subjected toextraction in chloroform at 60° C. for 5 hours to show no extraction ofPS-5.

(2) Determination of Structure of Polyacetal Copolymer

Hydrolysis of the polyacetal copolymer obtained in step (1) showed thatthe insertion ratio of oxyethylene units in this polymer was 1.5 mol per100 mol of oxymethylene units. The amount of PS-5 in this polymer was15.1×10⁻⁴ mol per mole of formaldehyde.

The terminal hydroxy group of the polyacetal copolymer obtained in step(1) was quantitatively determined by acetylation to show 20.2×10⁻⁴ molper mole of formaldehyde. This polymer was found to have an oxymethylenechain in which the number average molecular weight was 17,000 and whichhas the following structure: ##STR38##

The structural formula [(OCH₂)₅₆₇ (OCH₂ CH₂)₈ ] shows an insertion of 8mol of oxyethylene units into 567 mol of oxymethylene units and does notdefine a distribution of the oxyethylene units in the polymer chain.

The above polyacetal copolymer had the desired molecular weight and alsohad a reduced viscosity of 1.58, as expected. It also exhibited anR_(v222) of 98.7% and an excellent coatability of 12/100 in a crosscuttest (using a urethane-based coating composition).

EXAMPLE 6 (1) Production of Polyacetal Copolymer

A kneader having two Σ-formed stirring blades was charged with 500 g offully purified trioxane, 25 g of 1,4-butanediol formal and 150 g of amolecular weight regulator of ##STR39## (polystyrene whose one terminalportion was modified into hydroxyl, M_(n) =9,000, "PS-2" hereinafter),and the charged components were heated to 70° C. Then, the kneader wascharged with 0.25 g of boron trifluoride dibutyl etherate, and theresultant mixture was heated for 35 minutes. Immediately thereafter, 10g of tributylamine was added to terminate the polymerization. Thereaction mixture was taken out of the kneader and washed with hotacetone to give 460 g of a polyacetal copolymer. This polymer wassubjected to extraction in chloroform at 60° C. for 5 hours to show noextraction of PS-2.

(2) Determination of Production of Polyacetal Copolymer

Hydrolysis of the polyacetal copolymer obtained in step (1) showed thatthe insertion ratio of oxytetramethylene units in this polymer was 1.5mol per 100 mol of oxymethylene units. The amount of PS-2 in thispolymer was 7.67×10⁻⁴ mol per mole of formaldehyde.

The terminal hydroxy group of the polyacetal copolymer obtained in step(1) was quantitatively determined by acetylation to show 188×10⁻⁵ molper mole of formaldehyde. This polymer was found to have an oxymethylenechain in which the number average molecular weight was 31,800 and whichhas the following structure: ##STR40##

The structural formula of --OCH₂)₅₃₀ (OCH₂ CH₂ CH₂ CH₂)₈ ] shows aninsertion of 8 mol of oxytetramethylene units into 530 mol ofoxymethylene units and does not define a distribution of the oxyethyleneunits in the polymer chain.

The above polyacetal copolymer also exhibited an excellent coatabilityof 0/100 in the crosscut test (using an acrylic coating composition).

EXAMPLE 7

Example 5 was repeated except that a molecular weight regulator of##STR41## (acrylonitrile whose one terminal portion was modified intohydroxyl, M_(n) =24,000) was used in place of PS-5. The resultantpolymer had a reduced viscosity of 2.3 and an R_(v222) of 98.7%. It wasalso found to have a number average molecular weight of 89,000 and tohave the following structural formula: ##STR42##

The structural formula of --OCH₂)₅₃₃ (OCH₂ CH₂)₆ ] shows the insertionof 6 mol of oxyethylene units into 533 mol of oxymethylene units, anddoes not define a distribution of the oxymethylene units in the polymerchain.

The above polyacetal copolymer also exhibited an excellent coatabilityof 0/100 in the crosscut test (using an acrylic coating composition).

COMPARATIVE EXAMPLE 1

Example 1 was repeated except that a know molecular weight regulator,methanol, was used in place of PBA-9. The resultant polymer had areduced viscosity of 1.64 and an R_(v222) of 98.9%. It was also found tohave a number average molecular weight of 26,000. It had the structuralformula of CH₂ O--CH₂ O)₈₇₀ H.

A molded article therefrom was evaluated for coatability by the crosscuttest (using a urethane-based coating composition) and had a value of100/100, or no coatability.

COMPARATIVE EXAMPLE 2

Example 1 was repeated except that the following polymers having nofunctional group at one end were used in place of PBA-9:

(1) Vinyl acetate/methylacrylic acid copolymer, and

(2) Vinyoxyethylamine/isobutyl methacrylate copolymer.

The resultant polymers had a reduced viscosity of 0.8 in the case of (1)and a reduced viscosity of 1.1 in the case of (2). Each of moldedarticles therefrom was evaluated for Coatability by the crosscut test(using a urethane-based coating composition) and had a valve of 100/100,or no coatability.

Each of the polymers obtained in this Comparative Example was a graftcopolymer in which the trunk polymer was formed from a vinylacetate/methacrylic acid copolymer or from a vinyloxyethylamine/isobutylmethacrylate copolymer and the branch polymer was formed frompolyoxymethylene.

COMPARATIVE EXAMPLE 3

Example 5 was repeated except that a vinyl polymer having no functionalgroup at one end, i.e. Polymethyl methacrylate was used in place ofPS-5. The resultant polymer had a reduced viscosity of 0.7. This polymerwas evaluated for coatability by the crosscut test (using an acryliccoating composition) and had a value of 100/100, or no coatability.

The polymer obtained in this Comparative Example was a graft copolymerin which the trunk polymer was formed from polymethyl methacrylate andthe branch polymer was formed from polyoxymethylene.

EXAMPLES 8-31 AND COMPARATIVE EXAMPLES 4-9

Starting materials, cyclic ethers and molecular weight regulators shownin Table 1 were used to produce polyacetal copolymers shown in Table 2.Table 2 shows reduced viscosities, coatabilities (evaluated with anacrylic coating composition) and abrasion wear of the polyacetalcopolymers. In all of the Examples of the invention, the polyacetalcopolymers exhibited excellent coatability, and all of these polyacetalcopolymers were novel.

On the other hand, in Comparative Examples 4, 5, 6, and 7, the polymersexhibited no coatability. In Comparative Examples 8 and 9, the polymersexhibited poor mechanical properties although they had improvedcoatability.

In addition, of the molecular weight regulators shown in Table 1, thosehaving the following structure --C)_(q) (E)_(r) ] are copolymerscomposed of q mol of a monomer C and r mol of a monomer E (and thisdescription does not define any blocks of the C polymer and the Epolymer).

EXAMPLE 32 (1) Production of Polyacetal Resin Composition

(A) Polyacetal copolymer; the polyacetal copolymer produced in Example1.

(B) Polyvinyl polymer; a polymer having a weight average molecularweight of 150,000, obtained by polymerization of n-butyl acrylate in thepresence of AIBN (radical polymerization initiator).

(C) Polyoxymethylene; a polymer having an MI of 5.8 (g/10 minutes),obtained by homopolymerizing formaldehyde in the presence, as acatalyst, of dibutyltin methoxide (anionic polymerization catalyst) andstabilizing the terminal portion of the resultant polymer with aceticanhydride.

    ______________________________________                                        Polyacetal copolymer (A)                                                                        100      parts by weight                                    Polyvinyl polymer (B)                                                                           100      parts by weight                                    Polyoxymethylene (C)                                                                            50       parts by weight                                    Thermal stabilizer Nylon 66                                                                     0.5      part by weight                                     Antioxidant [2,2- 0.4      part by weight                                     methylenebis(4-methyl-                                                        6-tert-butylphenol,                                                           "OA" hereinafter)                                                             ______________________________________                                    

The above components were mixed, and then melted in a 30 mm-diametertwin-screw extruder.

(2) Physical Properties of Polyacetyl Resin Composition

The resultant polyacetal resin composition had excellent mechanicalproperties, i.e. MI of 4.2 (g/10 minutes) and an abrasion wear of1.2×10⁴ (g/km). This composition exhibited a crosscut test result of0/100 (the test using an acrylic coating composition), and thus it hadexcellent surface decorating properties.

EXAMPLE 33 (1) Production of Polyacetal Resin Composition

(A) Polyacetal copolymer; the polyacetal copolymer produced in Example2.

(B) Polyvinyl polymer; a polymer having a weight average molecularweight of 180,000, obtained by polymerization of iso-butyl methacrylatein the presence of AIBN.

(C) Polyoxymethylene; a polymer having an MI of 27.0 (g/10 minutes),obtained by copolymerizing trioxane and ethylene oxide in the presence,as a catalyst, of boron trifluoride (cationic polymerization catalyst)and stabilizing the resultant polymer by melting and hydrolyzing it inan extruder with triethylamine-water.

    ______________________________________                                        Polyacetal copolymer (A)                                                                       200       parts by weight                                    Polyvinyl polymer (B)                                                                          50        parts by weight                                    Polyoxymethylene (C)                                                                           100       parts by weight                                    Nylon 66         0.5       part by weight                                     AO               0.4       part by weight                                     ______________________________________                                    

The above components were mixed, and then melted in a 65 mm-diametertwin-screw extruder.

(2) Physical Properties of Polyacetal Resin Composition

The resultant polyacetal resin composition had excellent mechanicalproperties, i.e. an MI of 18.1 (g/10 minutes) and an abrasion wear of1.4×10⁻⁴ (g/km). This composition exhibited a crosscut test result of0/100 (the test using an acrylic coating composition), and was thereforefound to have excellent surface decorating properties.

EXAMPLE 34 (1) Production of Polyacetal Resin Composition

(A) Polyacetal copolymer; the polyacetal copolymer produced in Example3.

(B) Polyvinyl polymer; a polymer having a weight average molecularweight of 190,000, obtained by polymerization of methyl methacrylate inthe presence of AIBN.

(C) Polyoxymethylene; a polymer having an MI of 15.0 (g/10 minutes),obtained by copolymerizing trioxane and 1,4-butanediol formal oxide inthe presence, as a catalyst, of boron trifluoride dibutyl etherate(cationic polymerization catalyst) and stabilizing the resultant polymerby melting and hydrolyzing it in an extruder.

    ______________________________________                                        Polyacetal copolymer (A)                                                                       100       parts by weight                                    Polyvinyl polymer (B)                                                                          200       parts by weight                                    Polyoxymethylene (C)                                                                           300       parts by weight                                    Nylon 66         0.5       part by weight                                     AO               0.4       part by weight                                     ______________________________________                                    

The above components were mixed, and then melted in a 45 mm-diametertwin-screw extruder.

(2) Physical Properties of Polyacetal Resin Composition

The resultant polyacetal resin composition had excellent mechanicalproperties, i.e. an MI of 4.1 (g/10 minutes) and an abrasion wear of1.5×10⁻⁴ (g/km) This composition exhibited a crosscut test result of0/100 (the test using an acrylic coating composition), and was thereforefound to have excellent decorating properties.

EXAMPLE 35 (1) Production of Polyacetal Resin Composition

(A) Polyacetal copolymer; the polyacetal copolymer produced in Example4.

(B) Polyvinyl polymer; a polymer having a weight average molecularweight of 200,000, obtained by polymerization of styrene in the presenceOF AIBN.

    ______________________________________                                        Polyacetal copolymer (A)                                                                        100      parts by weight                                    Polyvinyl polymer (B)                                                                           50       parts by weight                                    Thermal stabilizer Nylon 66                                                                     0.5      part by weight                                     Antioxidant AO    0.4      part by weight                                     ______________________________________                                    

The above components were mixed, and then melted in a 30 mm-diametertwin-screw extruder to produce a polyacetal resin composition.

(2) Physical Properties of Polyacetal Resin Composition

The resultant polyacetal resin composition had excellent mechanicalproperties, i.e. an MI of 6.8 (g/10 minutes) and an abrasion wear of1.1×10⁻⁴ (g/km). This composition exhibited a crosscut test result of0/100 (the test using an acrylic coating composition), and thus hadexcellent surface decorating properties.

EXAMPLE 36 (1) Production of Polyacetal Resin Composition

(A) Polyacetal copolymer; the polyacetal copolymer produced in Example19.

(B) Polyvinyl polymer; a polymer having a weight average molecularweight of 250,000, obtained by copolymerization of methyl methacrylatean iso-butyl methacrylate in the presence of AIBN.

    ______________________________________                                        Polyacetal copolymer (A)                                                                       100       parts by weight                                    Polyvinyl polymer (B)                                                                          50        parts by weight                                    Nylon 66         0.5       part by weight                                     AO               0.4       part by weight                                     ______________________________________                                    

The above components were mixed, and then melted in a 65 mm-diametertwin-screw extruder to produce a polyacetal resin composition.

(2) Physical Properties of Polyacetal Resin Composition

The resultant polyacetal resin composition had excellent mechanicalproperties, i.e. an MI of 19.2 (g/10 minutes) and an abrasion wear of2.0×10⁻⁴ (g/km). This composition exhibited a crosscut test result of0/100 (the test using an acrylic coating composition), and was thereforefound to have excellent surface decorating properties.

EXAMPLE 37 (1) Production of Polyacetal Resin Composition

(A) Polyacetal copolymer; a polyacetal copolymer produced in Example 29.

(B) Polyvinyl polymer; a polymer having a weight average molecularweight of 170,000, obtained by copolymerization of acrylonitrile andstyrene in the presence of AIBN.

    ______________________________________                                        Polyacetal copolymer (A)                                                                       100       parts by weight                                    Polyvinyl polymer (B)                                                                          125       parts by weight                                    Nylon 66         0.5       part by weight                                     AO               0.4       part by weight                                     ______________________________________                                    

The above components were mixed, and then melted in a 45 mm-diametertwin-screw extruder to produce a polyacetal resin composition.

(2) Physical Properties of Polyacetal Resin Composition

The resultant polyacetal resin composition had excellent mechanicalproperties, i.e. an MI of 8.0 (g/10 minutes) and an abrasion wear of4.9×10⁻⁴ (g/km). This composition exhibited a crosscut test result of0/100 (the test using a two-package-curable acrylic coatingcomposition), and was thus found to have excellent surface decoratingproperties.

EXAMPLE 38 (1) Production of Polyacetal Resin Composition

(A) Polyacetal copolymer; the polyacetal copolymer produced in Example1.

(C) Polyoxymethylene; the polyoxymethylene produced in Example 32.

    ______________________________________                                        Polyacetal copolymer (A)                                                                       300       parts by weight                                    Polyoxmethylene (C)                                                                            100       parts by weight                                    Nylon 66         0.5       part by weight                                     AO               0.4       part by weight                                     ______________________________________                                    

The above components were melted in a 30 mm-diameter twin-screw extruderto produce a polyacetal resin composition.

(2) Physical Properties of Polyacetal Resin Composition

The resultant polyacetal resin composition had excellent mechanicalproperties, i.e. an MI of 12.3 (g/10 minutes) and an abrasion wear of15×10⁻⁴ (g/km). This composition exhibited a crosscut test result of0/100 (the test using an acrylic coating composition), and was thusfound to have excellent surface decorating properties.

EXAMPLES 39-70

(1) Production of Polyacetal Resin Compositions

(A) Polyacetal copolymers; respectively obtained by adding dibutyltindimethoxide, as a polymerization catalyst, to toluene containing apredetermined concentration of a polymer as a molecular weight regulatorshown in Table 3, then adding formaldehyde, separating the toluene andthe resultant polymer after a predetermined period of time, andstabilizing the polymer with acetic anhydride.

(B) Polyvinyl polymers; respectively obtained by homopolymerizing orcopolymerizing vinyl monomer(s) shown in Table 3 in the presence ofbenzoyl peroxide or AIBN.

(C) Polyoxymethylene; a polymer having an MI of 15.2 (g/10 minutes),obtained by homopolymerizing formaldehyde in the presence, as acatalyst, of dimethyldistearylammonium propionate (anionicpolymerization catalyst), and stabilizing the terminal portion of theresultant polymer with acetic anhydride.

The polyvinyl polymer (B) and the polyoxymethylene (C), of which theamounts (part by weight) are shown in Table 5, and 0.32 part by weightof a thermal stabilizer Nylon 66 and 0.4 part by weight of anantioxidant AO were added to 100 parts by weight of the polyacetalcopolymer (A), and these components were melt-mixed in a 30 mm-diametertwin-screw extruder.

(2) Physical Properties of Polyacetal Resin Compositions

Table 3 shows mechanical properties and results of a crosscut test(using an acrylic or urethane coating composition) of the compositionsproduced above. All of the compositions had excellent surface decoratingproperties and excellent mechanical properties in combination.

COMPARATIVE EXAMPLES 10-12

0.5 Part by weight of Nylon 66 and 0.4 part of AO were added to 100parts by weight of each of the polyoxymethylene obtained in the same wayas in Example 32, 33 and 34, and these components in each case weremelt-mixed with a 30 mm-diameter twin-screw extruder to obtaincompositions. Table 3 shows physical properties and crosscut testresults of the compositions. The coatability of each of thesecompositions was very poor.

COMPARATIVE EXAMPLES 13 and 14

A polyvinyl polymer synthesized from iso-butyl acrylate and apolyoxymethylene obtained in the same way as in Example 32 in theamounts shown in Table 3 were added to 100 parts by weight of the samepolyacetal copolymer as that obtained in Example 9, and 0.5 part ofNylon 66 and 0.4 part of AO were added. Then, these components weremelt-mixed with a 30 mm-diameter twin-screw extruder. Table 3 shows thephysical properties and the crosscut test results of the resultantcompositions.

The composition obtained in Comparative Example 13 had poor surfacedecorating properties since it contained an excess of thepolyoxymethylene.

The composition obtained in Comparative Example 14 had very poor surfacedecorating properties since it contained an excess of thepolyoxymethylene.

COMPARATIVE EXAMPLES 15 and 16

A polyvinyl polymer synthesized from methyl methacrylate and apolyoxymethylene obtained in the same way as in Example 33 in theamounts shown in Table 3 were added to 100 parts by weight of the samepolyacetal copolymer as that obtained in Example 12, and 0.5 part byweight of Nylon 66 and 0.4 part by weight of AO were added. Thesecomponents were melt-mixed with a 30 mm-diameter twin-screw extruder.Table 3 shows the physical properties and the crosscut test results ofthe resultant compositions.

These compositions had extraordinarily degraded mechanical propertiessince they contained an excess of the polyvinyl polymer.

REFERENTIAL EXAMPLE 1 (1) Production of Polyacetal Resin Composition

(B) Polyvinyl polymer; a polymer having a weight average molecularweight of 130,000, obtained by polymerizing methyl methacrylate in thepresence of AIBN (radical polymerization catalyst).

(C) Polyoxymethylene; the same polyoxymethylene as that produced inExample 32.

    ______________________________________                                        Polyoxymethylene (C)                                                                          100       parts by weight                                     Polyvinyl polymer (B)                                                                         20        parts by weight                                     Nylon 66        0.5       part by weight                                      AO              0.4       part by weight                                      ______________________________________                                    

These components were mixed, and then melted in a 30 mm-diametertwin-screw extruder.

(2) Physical Properties of Polyacetal Resin Composition

The resultant composition had poor mechanical properties, i.e. an MI of2.8 (g/10 minutes) and an abrasion wear of 9.7×10⁻³ (g/km). Further,this composition exhibited poor surface decorating properties, i.e. acrosscut test result of 100/100 (the test using an acrylic coatingcomposition). These poor properties were brought about by a phaseseparation of the polyvinyl polymer which resulted since the compositionwas a mere mixture of the polyoxymethylene with the polyvinyl polymer.

REFERENTIAL EXAMPLE 2

(B) Polyvinyl polymer; the same polyvinyl polymer as that produced inExample 33 (poly-iso-butyl methacrylate).

(C) Polyoxymethylene; the same polyoxymethylene as that produced inExample 32.

    ______________________________________                                        Polyoxymethylene (C)                                                                          100       parts by weight                                     Polyvinyl polymer (B)                                                                         10        parts by weight                                     Nylon 66        0.5       parts by weight                                     AO              0.4       parts by weight                                     ______________________________________                                    

These components were mixed, and then melted in a 30 mm-diametertwin-screw extruder.

(2) Physical Properties of Polyacetal Resin Composition

The resultant composition had poor mechanical properties, i.e. an MI of2.7 (g/10 minutes) and an abrasion wear of 6.1×10⁻³ (g/km). Further,this composition exhibited poor surface decorating properties, i.e. acrosscut test result of 100/100 (the test using an acrylic coatingcomposition). As described in Referential Example 1, these poorproperties were brought about by a phase separation of the polyvinylpolymer which resulted since the composition was a mere mixture of thepolyoxymethylene with the polyvinyl polymer.

In general, a molded article of a polyacetal resin has an inactivesurface, and therefore requires a primer treatment in order to decoratethe surface. In contrast, a molded article of the composition of thepolyacetal copolymer of this invention has unconventionally excellentsurface decorating properties. Such excellent properties are derivedfrom the following: In the polyacetal copolymer of this invention, thepolyacetal copolymer not only contains the vinyl polymer group (B) butalso has a structure in which polyoxymethylene is bonded to one terminalportion of the vinyl polymer group. In the composition of thisinvention, the polyacetal copolymer has the function of a compatibilizerlike that of the polyvinyl polymer and the polyoxymethylene.

                                      TABLE 1                                     __________________________________________________________________________    Example                                                                              Starting material                                                                      Cyclic ether                                                                             Molecular weight regulator                         __________________________________________________________________________    8      Formaldehyde                                                                             --                                                                                      ##STR43##                   Mn = 19,000           9      Formaldehyde                                                                             --                                                                                      ##STR44##                   Mn = 16,000           10     Formaldehyde                                                                             --                                                                                      ##STR45##                   Mn = 9,700            11     Formaldehyde                                                                             --                                                                                      ##STR46##                   Mn = 18,000           12     Formaldehyde                                                                             --                                                                                      ##STR47##                   Mn = 8,400            13     Formaldehyde                                                                             --                                                                                      ##STR48##                   Mn = 17,000           14     Formaldehyde                                                                             --                                                                                      ##STR49##                   Mn = 12,000           15     Formaldehyde                                                                             --                                                                                      ##STR50##                   Mn = 13,000           16     Formaldehyde                                                                             --                                                                                      ##STR51##                   Mn = 29,000           17     Formaldehyde                                                                             --                                                                                      ##STR52##                   Mn = 15,000           18     Formaldehyde                                                                             --                                                                                      ##STR53##                   Mn = 21,000           19     Formaldehyde                                                                             --                                                                                      ##STR54##                   Mn = 15,000           20     Formaldehyde                                                                             --                                                                                      ##STR55##                   Mn = 20,000           21     Formaldehyde                                                                             --                                                                                      ##STR56##                   Mn = 11,000           22     Formaldehyde                                                                             --                                                                                      ##STR57##                   Mn = 28,000           23     Formaldehyde                                                                           Ethylene oxide                                                                            ##STR58##                   Mn = 7,500            24     Formaldehyde                                                                           Ethylene oxide                                                                            ##STR59##                   Mn = 16,000           25     Trioxane     --                                                                                    ##STR60##                   Mn = 7,000            26     Trioxane      --                                                                                   ##STR61##                   Mn = 6,500            27     Trioxane Ethylene oxide                                                                            ##STR62##                   Mn = 7,000            28     Trioxane Ethylene oxide                                                                            ##STR63##                   Mn = 12,000           29     Trioxane Ethylene glycol formal                                                                    ##STR64##                   Mn = 50,000           30     Trioxane Ethylene oxide                                                                            ##STR65##                   Mn = 14,000           31     Trioxane 1,4-Butanediol formal                                                                     ##STR66##                   Mn = 24,000           Comparative                                                                          Formaldehyde                                                                             --       H.sub.2 O                                          Example 4                                                                     Comparative                                                                          Formaldehyde                                                                             --       C.sub.2 H.sub.5 OH                                 Example 5                                                                     Comparative                                                                          Formaldehyde                                                                             --       HO(CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2                                        O).sub.50 H                                        Example 6                  Polytetramethylene glycol                          Comparative                                                                          Formaldehyde                                                                             --       HO(CH.sub.2 CH.sub.2 O).sub.50 H                   Example 7                  Polyethylene glycol                                Comparative Example 8                                                                Formaldehyde                                                                             --                                                                                      ##STR67##                   Mn = 16,000           Comparative Example 9                                                                Formaldehyde                                                                             --                                                                                      ##STR68##                   Mn                    __________________________________________________________________________                                                            = 29,000          

                                      TABLE 2                                     __________________________________________________________________________                                                Reduced                                                                             Abrasion                                                                             Crosscut             Example                                                                              Structure and Mn of polyacetal copolymer                                                                           viscosity                                                                           wear (gr/km)                                                                         test                 __________________________________________________________________________     8                                                                                    ##STR69##                           2.1   2.3 × 10.sup.-4                                                                0/100                 9                                                                                    ##STR70##                           2.0   1.1 × 10.sup.-4                                                                0/100                10                                                                                    ##STR71##                           1.8   3.2 × 10.sup.-4                                                                0/100                11                                                                                    ##STR72##                           2.3   5.1 × 10.sup.-4                                                                0/100                12                                                                                    ##STR73##                           1.9   0.8 × 10.sup.-4                                                                0/100                13                                                                                    ##STR74##                           2.0   5.6 × 10.sup.-4                                                                0/100                14                                                                                    ##STR75##                           1.6   0.8 × 10.sup.-4                                                                0/100                15                                                                                    ##STR76##                           1.7   4.3 × 10.sup.-4                                                                0/100                16                                                                                    ##STR77##                           2.2   2.8 × 10.sup.-4                                                                0/100                17                                                                                    ##STR78##                           4.3   1.6 × 10.sup.-4                                                                0/100                18                                                                                    ##STR79##                           3.9   2.1 × 10.sup.-4                                                                0/100                19                                                                                    ##STR80##                           1.5   2.9 × 10.sup.-4                                                                0/100                20                                                                                    ##STR81##                           1.9   1.7 × 10.sup.-4                                                                0/100                21                                                                                    ##STR82##                           2.1   3.6 × 10.sup.-4                                                                0/100                22                                                                                    ##STR83##                           2.6   2.2 × 10.sup.-4                                                                4/100                23                                                                                    ##STR84##                           1.5   4.1 × 10.sup.-4                                                                8/100                24                                                                                    ##STR85##                           2.0   1.3 × 10.sup.-4                                                                3/100                25                                                                                    ##STR86##                           1.8   2.2 × 10.sup.-4                                                                3/100                26                                                                                    ##STR87##                           1.8   4.8 × 10.sup.-4                                                                1/100                27                                                                                    ##STR88##                           1.5   5.1 × 10.sup.-4                                                                0/100                28                                                                                    ##STR89##                           1.7   2.7 × 10.sup.-4                                                                0/100                29                                                                                    ##STR90##                           4.7   0.7 × 10.sup.-4                                                                0/100                30                                                                                    ##STR91##                           2.3   1.6 × 10.sup.-4                                                                0/100                31                                                                                    ##STR92##                           3.3   2.2 × 10.sup.-4                                                                0/100                Comparative Example 4                                                                 ##STR93##                           1.8   1.2 × 10.sup.-4                                                                100/100              Comparative Example 5                                                                 ##STR94##                           1.6   1.2 × 10.sup.-4                                                                100/100              Comparative Example 6                                                                 ##STR95##                           1.8   2.9 × 10.sup.-4                                                                100/100              Comparative Example 7                                                                 ##STR96##                           2.0   0.8 × 10.sup.-4                                                                100/100              Comparative Example 8                                                                 ##STR97##                           2.3   9.7 × 10.sup.-2                                                                48/100               Comparative Example 9                                                                 ##STR98##                           2.1   8.2 × 10.sup.-2                                                                51/100               __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________                                  Polyacetal resin                                                              composition                                                                   Poly-                                                                              polyoxy-                                                                           Abrasion                                                                            Cross-                          Ex-                           vinyl                                                                              methyl-                                                                            wear  cut                             ample  Polymer *note)                                                                            Vinyl monomer                                                                            polymer                                                                            ene  gr/km test                            __________________________________________________________________________    39     Polyethyl acrylate                                                                        Ethyl acrylate                                                                            5    0   1.1 × 10.sup.-4                                                               0/100                                  (--COOH)                                                               40     Polyisobutyl meth-                                                                        Isobutyl meth-                                                                            30   0   2.1 × 10.sup.-4                                                               0/100                                  acrylate (--OH)                                                                           acrylate                                                   41     Isobutyl methacrylate/                                                                    Isobutyl meth-                                                                            50   0   3.1 × 10.sup.-4                                                               0/100                                  methyl methacrylate                                                                       acrylate Methyl                                                   copolymer (2-OH)                                                                          methacrylate                                               42     Methyl methacrylate/                                                                      Methyl methacrylate                                                                      200   0   2.8 × 10.sup.-4                                                               0/100                                  n-butyl acrylate                                                                          n-butyl meth-                                                     copolymer (2-OH)                                                                          acrylate                                                   43     2-Ethylhexyl meth-                                                                        2-Ethylhexyl meth-                                                                       400   0   5.1 × 10.sup.-4                                                               0/100                                  acrylate/methyl                                                                           acrylate Methyl                                                   methacrylate copolymer                                                                    methacrylate                                                      (3-COOH)                                                               44     n-Stearyl methacrylate/                                                                   N-Stearyl meth-                                                                          500   0   8.8 × 10.sup.-4                                                               0/100                                  Styrene copolymer                                                                         acrylate                                                          (2-OH)      Styrene                                                    45     Poly-n-butyl acrylate                                                                     n-Butyl acrylate                                                                         100   0   1.8 × 10.sup.-4                                                               0/100                                  (--OH)      Methyl methacrylate                                        46     Isobutyl methacrylate/                                                                    Methyl methacrylate                                                                      250   0   1.9 × 10.sup.-4                                                               0/100                                  methyl methacrylate                                                           copolymer (2-OH)                                                       47     n-Octyl methacrylate/                                                                     n-Octyl meth-                                                                            300   0   3.2 × 10.sup.-4                                                               0/100                                  methyl methacrylate                                                                       acrylate                                                          copolymer (2-COOH)                                                     48     Polyisobutyl meth-                                                                        Iosbutyl meth-                                                                            10   5   1.8 × 10.sup.-4                                                               0/100                                  acrylate copolymer                                                                        acrylate                                                          (2-OH)                                                                 __________________________________________________________________________     Note)                                                                         Functional group(s) in one terminal is in parenthesis. For example (--OH)     means one --OH group, (2OH) meand two --OH groups, and (3OH) means three      --OH groups. In the following Tables, the group(s) in parenthesis have th     same meaning.                                                            

    Polyacetal resin                                                                                            composition                                            Polymer                Poly-                                                                              polyoxy-                                                                           Abrasion                                                                            Cross-                          Ex-    (one-terminal          vinyl                                                                              methyl-                                                                            wear  cut                             ample  functional group)                                                                         Vinyl monomer                                                                            polymer                                                                            ene  gr/km test                            __________________________________________________________________________    49     Poly-n-butyl acrylate                                                                     n-Butyl acrylate                                                                          30   50  3.3 × 10.sup.-4                                                               0/100                                  (2-OH)      Methyl methacrylate                                        50     Poly-iso-butyl                                                                            Isobutyl meth-                                                                           100  100  2.7 × 10.sup.-4                                                               0/100                                  methyacrylate (--OH)                                                                      acrylate                                                   51     Isobutyl methacrylate/                                                                    Isobutyl meth-                                                                           100  300  3.0 × 10.sup.-4                                                               0/100                                  methyl methacrylate                                                                       acrylate Methyl                                                   copolymer (2-NH.sub.2)                                                 52     Acrylonitrile/methyl                                                                      Acrylonitrile                                                                            100  500  2.7 × 10.sup.-4                                                               3/100                                  acrylate copolymer                                                                        Methyl methacrylate                                               (2-NH.sub.2)                                                           53     Vinyl chloride/methyl                                                                     Vinyl chloride,                                                                          350  500  3.6 × 10.sup.-4                                                               0/100                                  acrylate/methyl                                                                           methyl meth-                                                      copolymer (--OH)                                                                          acrylate, methyl                                                              methacrylate                                               54     Styrene/acrylonitrile                                                                     Styrene    500  500  9.9 × 10.sup.-4                                                               0/100                                  copolymer (2-OH)                                                                          Acrylonitrile                                              55     Polyisobutyl meth-                                                                        Isobutyl   200  500  3.2 × 10.sup.-4                                                               0/100                                  acrylate (2-OH)                                                                           methacrylate                                               56     Polyisobutyl meth-                                                                        Isobutyl   200  800  3.7 × 10.sup.-4                                                               0/100                                  acrylate (2-OH)                                                                           methacrylate                                               57     Polyisobutyl meth-                                                                        Isobutyl   200  1100 2.9 × 10.sup.-4                                                               2/100                                  acrylate (2-OH)                                                                           methacrylate                                               58     Polyisobutyl meth-                                                                        Isobutyl   200  1500 3.1 × 10.sup.-4                                                               4/100                                  acrylate (2-OH)                                                                           methacrylate                                               59     n-Lauryl methacrylate/                                                                    n-Lauryl meth-                                                                           100  200  1.9 × 10.sup.-4                                                               0/100                                  methyl methacrylate                                                                       acrylate methyl                                                   copolymer (2-COOH)                                                                        methacrylate                                               60     n-Lauryl methacrylate/                                                                    n-Lauryl meth-                                                                           200  200  2.1 × 10.sup.-4                                                               0/100                                  methyl methacrylate                                                                       acrylate methyl                                                   copolymer (2-COOH)                                                                        methacrylate                                               61     n-Lauryl methacrylate/                                                                    n-Lauryl meth-                                                                           300  200  4.9 × 10.sup.-                                                                0/100                                  methyl methacrylate                                                                       acrylate methyl                                                   copolymer (2-COOH)                                                                        methacrylate                                               62     n-Lauryl methacrylate/                                                                    n-Lauryl meth-                                                                           500  200  7.0 × 10.sup.-4                                                               0/100                                  methyl methacrylate                                                                       acrylate methyl                                                   copolymer (2-COOH)                                                                        methacrylate                                               63     Styrene/methyl                                                                            Styrene     0    5   1.4 × 10.sup.-4                                                               3/100                                  methacrylate copolymer                                                                    Methyl methacrylate                                               (3-OH)                                                                 64     Poly-n-propyl                                                                             n-Propyl meth-                                                                            0    50  1.6 × 10.sup.-4                                                               0/100                                  methacrylate (3-NH.sub.2)                                                                 acrylate                                                   65     iso-Stearyl meth-                                                                         iso-Stearyl meth-                                                                         0   200  1.1 × 10.sup.-4                                                               0/100                                  acrylate/methyl                                                                           acrylate methyl                                                   methacrylate copolymer                                                                    methacrylate                                                      (--OH)                                                                 66     Acrylonitrile/vinyl                                                                       Acrylonitrile vinyl                                                                       0   500  0.9 × 10.sup.-4                                                               1/100                                  chloride copolymer                                                                        chloride                                                          (2-COOH)                                                               67     Ethyl methacrylate/                                                                       Ethyl methacrylate                                                                        0   800  1.5 × 10.sup.-4                                                               0/100                                  styrene copolymer                                                                         styrene                                                           (2-COOH)                                                               68     Polymethyl meth-                                                                          Methyl meth-                                                                              0   1000 1.8 × 10.sup.-4                                                               3/100                                  acrylate (--OH)                                                                           acrylate                                                   69     n-Butyl methacrylate/                                                                     n-Butyl meth-                                                                             0   1500 2.6 × 10.sup.-4                                                               5/100                                  iso-butyl methacrylate                                                                    acrylate iso-                                                     copolymer (--OH)                                                                          butyl methacrylate                                         70     n-Butyl methacrylate/                                                                     n-Butyl meth-                                                                             0   1650 2.7 × 10.sup.-4                                                               11/100                                 iso-butyl methacrylate                                                                    acrylate iso-                                                     copolymer (--OH)                                                                          butyl methacrylate                                         Comparative                                                                          --          --         --   --   3.3 × 10.sup.-4                                                               100/100                         Example 10                                                                    Comparative                                                                          --          --         --   --   2.1 × 10.sup.-4                                                               100/100                         Example 11                                                                    Comparative                                                                          --          --         --   --   1.7 × 10.sup.-4                                                               100/100                         Example 12                                                                    Comparative                                                                          --          --         300  1800 1.1 × 10.sup.-4                                                               31/100                          Example 13                                                                    Comparative                                                                          --          --          0   1800 0.8 × 10.sup.-4                                                               82/100                          Example 14                                                                    Comparative                                                                          --          --         650   0   9.8 × 10.sup.-3                                                               0/100                           Example 15                                                                    Comparative                                                                          --          --         700  500  5.1 × 10.sup.-3                                                               0/100                           Example 16                                                                    __________________________________________________________________________

INDUSTRIAL UTILITY

The polyacetal copolymer provided by this invention and the compositionof this invention comprising the polyacetal copolymer and the specifiedother resins are engineering resins useful in a wide range of industrialfields such as in the automobile part field, etc., since they are notonly excellent in physical properties such as mechanical strength andelectrical properties but they are also excellent with respect tosurface decorating properties such as printing and coating. The processfor the production of the polyacetal copolymer, provided by thisinvention, gives the above excellent resins.

What is claimed is:
 1. A polyacetal copolymer having a number averagemolecular weight of 10,000 to 500,000 of the formula ##STR99## whereinR₁ is hydrogen or alkyl;R₂ is phenyl, cyano, chloro, acetyl or alkylester; l is 10 to 5,000; A is polyoxymethylene; D is ##STR100## Y isoxygen or sulfur; and a is 0 to
 3. 2. The polyacetal copolymer accordingto claim 1, wherein the vinyl group (B) is a residue of a poly(meth)acrylate ester.
 3. The polyacetal copolymer according to claim 1,wherein the vinyl group (B) is a residue of a copolymer of an acrylateester and a methacrylate ester.
 4. The polyacetal copolymer according toclaim 1, wherein the vinyl group (B) is a residue of a polystyrene. 5.The polyacetal copolymer according to claim 1, wherein the vinyl group(B) is a residue of a copolymer of styrene and an (meth)acrylate ester.6. The polyacetal copolymer according to claim 1, wherein theoxyalkylene unit is an oxyethylene unit.
 7. The polyacetal copolymeraccording to claim 1, wherein the oxyalkylene unit is anoxytetramethylene unit.